/*
 * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/AutoCloseInputStream.java,v 1.9 2004/04/18 23:51:34 jsdever Exp $
 * $Revision: 505890 $
 * $Date: 2007-02-11 12:25:25 +0100 (Sun, 11 Feb 2007) $
 *
 * ====================================================================
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.commons.httpclient;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Closes an underlying stream as soon as the end of the stream is reached, and
 * notifies a client when it has done so.
 * 
 * @author Ortwin Glueck
 * @author Eric Johnson
 * @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
 * 
 * @since 2.0
 */
class AutoCloseInputStream extends FilterInputStream {

	/**
	 * True if this stream is open. Assume that the underlying stream is open
	 * until we get an EOF indication.
	 */
	private boolean streamOpen = true;

	/** True if the stream closed itself. */
	private boolean selfClosed = false;

	/**
	 * The watcher is notified when the contents of the stream have been
	 * exhausted
	 */
	private ResponseConsumedWatcher watcher = null;

	/**
	 * Create a new auto closing stream for the provided connection
	 * 
	 * @param in
	 *            the input stream to read from
	 * @param watcher
	 *            To be notified when the contents of the stream have been
	 *            consumed.
	 */
	public AutoCloseInputStream(final InputStream in,
			final ResponseConsumedWatcher watcher) {
		super(in);
		this.watcher = watcher;
	}

	/**
	 * Reads the next byte of data from the input stream.
	 * 
	 * @throws IOException
	 *             when there is an error reading
	 * @return the character read, or -1 for EOF
	 */
	public int read() throws IOException {
		int l = -1;

		if (isReadAllowed()) {
			// underlying stream not closed, go ahead and read.
			l = super.read();
			checkClose(l);
		}

		return l;
	}

	/**
	 * Reads up to <code>len</code> bytes of data from the stream.
	 * 
	 * @param b
	 *            a <code>byte</code> array to read data into
	 * @param off
	 *            an offset within the array to store data
	 * @param len
	 *            the maximum number of bytes to read
	 * @return the number of bytes read or -1 for EOF
	 * @throws IOException
	 *             if there are errors reading
	 */
	public int read(byte[] b, int off, int len) throws IOException {
		int l = -1;

		if (isReadAllowed()) {
			l = super.read(b, off, len);
			checkClose(l);
		}

		return l;
	}

	/**
	 * Reads some number of bytes from the input stream and stores them into the
	 * buffer array b.
	 * 
	 * @param b
	 *            a <code>byte</code> array to read data into
	 * @return the number of bytes read or -1 for EOF
	 * @throws IOException
	 *             if there are errors reading
	 */
	public int read(byte[] b) throws IOException {
		int l = -1;

		if (isReadAllowed()) {
			l = super.read(b);
			checkClose(l);
		}
		return l;
	}

	/**
	 * Obtains the number of bytes that can be read without blocking.
	 * 
	 * @return the number of bytes available without blocking
	 * @throws IOException
	 *             in case of a problem
	 */
	public int available() throws IOException {
		int a = 0; // not -1

		if (isReadAllowed()) {
			a = super.available();
			// no checkClose() here, available() can't trigger EOF
		}

		return a;
	}

	/**
	 * Close the stream, and also close the underlying stream if it is not
	 * already closed.
	 * 
	 * @throws IOException
	 *             If an IO problem occurs.
	 */
	public void close() throws IOException {
		if (!selfClosed) {
			selfClosed = true;
			notifyWatcher();
		}
	}

	/**
	 * Close the underlying stream should the end of the stream arrive.
	 * 
	 * @param readResult
	 *            The result of the read operation to check.
	 * @throws IOException
	 *             If an IO problem occurs.
	 */
	private void checkClose(int readResult) throws IOException {
		if (readResult == -1) {
			notifyWatcher();
		}
	}

	/**
	 * See whether a read of the underlying stream should be allowed, and if
	 * not, check to see whether our stream has already been closed!
	 * 
	 * @return <code>true</code> if it is still OK to read from the stream.
	 * @throws IOException
	 *             If an IO problem occurs.
	 */
	private boolean isReadAllowed() throws IOException {
		if (!streamOpen && selfClosed) {
			throw new IOException("Attempted read on closed stream.");
		}
		return streamOpen;
	}

	/**
	 * Notify the watcher that the contents have been consumed.
	 * 
	 * @throws IOException
	 *             If an IO problem occurs.
	 */
	private void notifyWatcher() throws IOException {
		if (streamOpen) {
			super.close();
			streamOpen = false;

			if (watcher != null) {
				watcher.responseConsumed();
			}
		}
	}
}
